1. Field of the Invention
The present invention relates generally to press force severity monitoring and, more particularly to utilizing monitored force severity to determine impulse energy for the purpose of determining the effects of any press/die application on the long-term operating reliability of a press during production operation.
2. Description of the Related Art
Mechanical presses of the type performing stamping and drawing operations employ a conventional construction that includes a frame structure having a crown and a bed portion and which supports a slide in a manner enabling reciprocating movement toward and away from the bed. These press machines are widely used for a variety of workpiece operations employing a large selection of die sets with the press machine varying considerably in size and available tonnage depending upon its intended use.
The press machine applies force to a workpiece so that the stock material acquires the desired formation which corresponds to the die set being utilized. Systems for monitoring press operating reliability assist the press owner in evaluating the severity of certain die/load applications on the reliability of the press being monitored. Conventional monitoring systems include systems which monitor the peak load being developed within certain components of the press machine during a slide stroke of the press. These monitored peak load levels are then compared with historical peak load level measurements or reference peak load levels.
Known load monitoring systems include systems which indicate the loads on presses and automatically detect if the load incurred by the force carrying member exceeds a predetermined value or is below a predetermined value.
Monitoring the maximum loads exerted on load bearing members during a slide stroke of a mechanical press allows press and die applications to be adjusted when monitored peak load values are outside the identified range. However, monitoring peak load is not an accurate operating reliability indicator since peak load does not account for multiple load peaks, peak loads which occur more than once during a press cycle, both compressive and tensile loads, multiple compressive or tensile peaks, or impulse energy.
The present invention is directed to improve upon the aforementioned method and means of monitoring the operating reliability of a mechanical press, wherein it is desired to monitor the operating reliability of a mechanical press in such a way so as to account for both compressive and tensile loads, multiple peak compressive and tensile loads, and impulse energy.
The present invention provides a method and apparatus for monitoring the long-term operating reliability of a mechanical press during its production operation which measures load over time and utilizes impulse energy as a measure of the operating condition of the mechanical press.
The invention, in one form thereof, comprises a load sensor which senses compressive and tensile loads and is affixed to a load bearing member of a mechanical press, and a computational device for receiving the load value from the load sensor and computing a measure of the impulse energy for one slide stroke of the running press. The computational device can be, for example, a microprocessor.
The invention, in another form thereof, includes a load sensor which senses compressive and tensile loads and is affixed to a load bearing member of the running press, and a computational device for receiving the load value from the load sensor and computing a measure of the impulse energy created by both compressive and tensile forces experienced during one slide stroke of the running press.
The invention, in another form thereof, includes a load sensor which senses compressive and tensile loads and is affixed to a load bearing member of a running press, and a computational device for receiving the load value from the load sensor and computing a reference impulse energy value for one slide stroke of the mechanical press. The reference impulse energy value can be, for example, a reference value which corresponds to a slow speed operation of the running press, a reference value which corresponds to a normal production operation of the mechanical press, or a reference value which corresponds to a particular die set which is used with the mechanical press.
The invention, in another form thereof, comprises a load sensor which senses compressive and tensile loads and is affixed to a load bearing member of a running press, and a computational device for receiving the load value from the load sensor and storing a reference impulse energy value. The computational device computes the total impulse energy for one slide stroke of the running press, which includes the impulse energy created by both compressive and tensile forces. The computational device also computes a ratio of the total impulse energy for one slide stroke to the reference impulse energy value.
The invention, in another form thereof, comprises a load sensor for sensing compressive and tensile loads which is affixed to a load bearing member of the running press and a computational device which computes values of impulse energy for one slide stroke of the mechanical press. The computed value of impulse energy can be, for example, a measure of the impulse energy corresponding to the compressive load sensed by the load sensor, a measure of the impulse energy corresponding to the tensile load sensed by the load sensor, or a total measure of the impulse energy which includes both the impulse energy associated with the compressive load and the tensile load sensed by the load sensor.
The invention, in another form thereof, comprises a load sensor for sensing compressive and tensile loads which is affixed to a load bearing member of a running press and a computational device for computing impulse energy values for one slide stroke of the running press. The impulse energy values computed by the computational device may be, for example, the impulse energy corresponding to the compressive load sensed by the load sensor, the impulse energy corresponding to the tensile load sensed by the load sensor, or the total impulse energy corresponding to both the compressive load and tensile load sensed by the load sensor for one slide stroke. In this form, the computational device may also be utilized for computing reference impulse energy values, including reference impulse energy values corresponding to normal production operation, slow speed operation, or a particular die set used with the running press. The computational device may further be used to compute a ratio of monitored impulse energy to a reference impulse energy value. The values computed in the computational device may be communicated to, for example, a digital storage device, a modem, a display device, an alert device or a shutoff device. The digital storage may be utilized for compiling histories of impulse energy values and their corresponding ratios to a reference impulse energy value. A modem may be used for communicating impulse energy values and/or their relation to a reference impulse energy value to a remote location. The display device may display monitored impulse energy and/or the ratio of the monitored impulse energy to a reference value so that service personnel may determine how features such as press speed, shut height and the die setup alter the operational condition of the running press. The alert device and the shutoff device will produce an alert signal and discontinue press operation, respectively, if the impulse energy value and/or the ratio of impulse energy value to a reference impulse energy value exceeds a predetermined measure.
The invention, in another form thereof, comprises a method of monitoring the reliability condition of a running press by monitoring the impulse energy of the running press and comparing the monitored impulse energy of the running press to a reference impulse energy value.
The invention, in another form thereof, comprises a method of monitoring the impulse energy of a running press. This method includes the steps of: placing a load sensor on a load bearing member of the running press, providing a computational device, communicating the load sensed by the load sensor to the computational device, plotting the sensed load value versus time and computing a value of impulse energy for one slide stroke of the running press using the sensed load value versus time curve.
The invention, in another form thereof, comprises a method of monitoring the reliability condition of a running press. This method includes the steps of: placing a load sensor on a load bearing member of the running press, providing a computational device, communicating the load sensed by the load sensor to the computational device, computing the absolute value of the sensed load values, plotting the absolute values of the sensed load values versus time and computing the area under the sensed load value versus time curve.
The invention, in another form thereof, comprises a method of monitoring the reliability condition of a running press. This method includes the steps of: monitoring the impulse energy of the running press. In this form, the step of monitoring the impulse energy of the running press includes: placing a load sensor on a load bearing member of the running press, providing a computational device, communicating the load sensed by the load sensor to the computational device, plotting sensed load values versus time, and computing a value of impulse energy for one slide stroke of the running press using the sensed load value versus time curve. In this form, the step of computing the value of impulse energy for one slide stroke of the running press comprises, for example, computing a value of tensile impulse energy, computing a value of compressive impulse energy or computing a total value of impulse energy for one slide stroke of the running press. The step of computing a value of tensile impulse energy includes: plotting the sensed tensile load versus time and computing the area under the sensed tensile load versus time curve. In this form, the step of computing a value of compressive impulse energy comprises: computing the absolute value of the sensed compressive load values, plotting the absolute values of the sensed compressive load values versus time, and computing the area under the sensed compressive load value versus time curve. The step of computing a total value of impulse energy for one slide stroke of the running press includes: computing the absolute value of the sensed load values, plotting the absolute values of the sensed load values versus time and computing the area under the sensed load value versus time curve.
The invention, in another form thereof, comprises a method of monitoring the reliability condition of a running press. This method includes the steps of: monitoring the impulse energy of the running press, determining a reference impulse energy value and computing a ratio of the monitored impulse energy for one slide stroke of the running press to the reference impulse energy for one slide stroke of the running press. The step of determining a reference impulse energy value includes: establishing a reference impulse energy value which corresponds, for example, to a slow speed operation of the running press, to a normal production operation of the running press, or to a particular die set used with the running press.
An advantage of the present invention is that monitoring of impulse energy provides a reliable indicator of mechanical press operating reliability.
Another advantage of the present invention is that multiple peaks in loads which occur during a pressing operation may be accounted for in determining the operating reliability of a mechanical press.
Another advantage of the present invention is that both compressive and tensile loads can be accounted for in determining the operating reliability of a mechanical press.
Another advantage of the present invention is that additional force severity activity which is due to multiple load peaks of either compressive or tensile loads can be accounted for in determining the operating reliability of a mechanical press.
A further advantage of the present invention is that impulse energy can be used to create a relative application severity reference signal which does not relate to actual peak load level.